Alternative Control Strategies for Termites

Vernard R. Lewis

Division of Insect Biology

Department of Environmental Science, Policy and Management

University of California

Berkeley, California 94720 USA

ABSTRACT The relative efficacy of five detection and 12 control methods for termites are reviewed. Chemical and nonchemical control methods are included. Discussions of the latest advances in detection and control focus on seven species: Cryptotermes brevis (Walker), Incisitermes minor (Hagen), I. snyderi (Light), Coptotermes formosanus Shiraki, Heterotermes aureus (Snyder), Reticulitermes flavipes (Kollar), and R. hesperus Banks. These species were chosen because they have great economic importance as pests and also have published studies on alternative control strategies. Tables and discussions recount the historical development as well as strengths and limitations for most termite detection and control methods. Differences between whole-structure and localized treatments also are discussed. Chemical methods are the most predominant termite treatment application. However, uses of alternative methods that emphasize least-toxic and nonchemical applications are increasing. Technological advances in detection are needed to enhance all termite control methods, especially those directed at localized applications. Prospects for the development and public acceptance of alternative termite controls appear good. Although, population reduction of termites from structures may be a more attainable and realistic goal than elimination as new technologies are developed. The greatest challenges ahead in improving and developing existing and new termite detection and control strategies will be to secure funds for research, and to identify mechanisms for rapid dissemination of evolving information to pest control operators and consumers.

KEY WORDS alternative termite control, chemical termite control, nonchemical termite control, Isoptera, Rhinotermitidae, subterranean termite, Kalotermitidae, drywood termite

Of the approximately 2,200 recognized species of termites worldwide, 45 occur in North America (Weesner 1965, Su & Scheffrahn 1990a). However, recent investigations involving cuticular hydrocarbons suggest there may be considerably more species diversity, at least in Reticulitermes (Haverty et al. 1996, Haverty & Nelson 1997). The economically important species in North America can be classified into three ecological groups: dampwood termites- Zootermopsis angusticollis (Hagen), Z. nevadensis (Hagen); drywood termites- Cryptotermes brevis (Walker), C. cavifrons Banks, Incisitermes minor (Hagen), I. snyderi (Light), I. schwarzi (Banks), Kalotermes approximatus Snyder, Marginitermes hubbardi (Banks), Neotermes castaneus (Burmeister), N. jouteli (Banks), Paraneotermes simplicicornis (Banks), P. occidentis (Walker); and subterranean termites- Coptotermes formosanus Shiraki, Heterotermes aureus (Snyder), Prorhinotermes simplex (Hagen), Reticulitermes arenincola Goellner, R. flavipes (Kollar), R. hageni Banks, R. hesperus Banks, R. tibialis Banks, R. virginicus Banks, Amitermes coachellae Light, A. emersoni Light, A. minimus Light, A. snyderi Light, A. wheeleri (Desneux), Gnathamitermes perplexus (Banks), G. tubiformans (Buckley), and Tenuirostritermes cinereus (Buckley) (Su & Scheffrahn 1990a). The major difference among dampwood, drywood, and subterranean groups is the requirement of contact of either soil or moisture by subterranean species. Dampwood termites are primarily restricted to fallen logs rotting on the forest floor while drywood termites do not require contact with soil or moisture for survival. Only those species listed as having great economic importance and published studies on alternative control strategies, Cryptotermes brevis (Walker), Incisitermes minor (Hagen), I. snyderi (Light), Coptotermes formosanus Shiraki, Heterotermes aureus (Snyder), Reticulitermes flavipes (Kollar), and R. hesperus Banks (Su & Scheffrahn 1990a), are included in this review.

The damage to wooden structures attributed to termites is significant and can exceed $ 3 billion annually, although estimates vary considerably by region (Su & Scheffrahn 1990a). Subterranean termites account for at least 80% of the losses; drywood termites account for less than 20% (Su & Scheffrahn 1990a).

The intent of this paper is to review the important advances in termite detection and control and provide general information on their relative efficacy. For the purposes of this paper, only general references to efficacy, effective, ineffective or mixed results and original author citation will be made. Since the mode of action, application, and treatment protection time vary considerably among treatment methods, specific references to numeric efficacy levels can not be made at this time. For example, fumigation is tremendously effective but the structure is vulnerable as soon as the fumigant dissipates from the building. While some localized treatment strategies require continual vigilance, such as baits, for remedial and preventive control. From the pest control provider's perspective, the goal of a treatment is to protect the structure. This can be accomplished by elimination or simply by trimming back the termite population.

In the discussion on alternative control strategies, chemical and nonchemical methods are included. For the most part, selected academically oriented papers and review articles are cited. Some reports and trade magazine features also are mentioned; but testimonial and marketing documents were avoided. Efficacy of pressure-treated wood for termite prevention (Rust & Scheffrahn 1982, Tamashiro et al. 1988, Grace et al. 1993a, Grace 1997), effectiveness of termite resistant woods (Grace et al. 1989a, Scheffrahn 1991, Grace & Yamamoto 1994, Delate & Grace 1995), and use of biological control agents (Mauldin & Beal 1989, Su & Scheffrahn 1990a, Delate et al. 1995a) are not reviewed in this paper and the reader can consult the aforementioned citations on these topics.

Termite Detection

Before a termite infested structure can be treated, some assessment of the extent of the infestation must be made. Visual searching and probing of wood is the dominant means of inspecting for termites (Scheffrahn et al. 1993). Within California alone, more than 1.5 million inspections are conducted yearly (Lewis & Lemaster 1991). However, the efficiency of visual searches is currently not known. The use of borescopes, a fiber optically based visual search aid, is also marketed. The efficiency of this visual search method for termite detection has yet to be scientifically tested.

Several nonvisual detection methods are being marketed. They include electronic stethoscopes,

dogs, and methane gas detectors. All detection technologies have limitations, and care must be shown in their selection (Potter 1997a). Acoustic emission (AE) detection has shown promise in laboratory and field investigations (Fujii et al. 1990, Scheffrahn et al. 1993, Hyvernaud et al. 1996, Lemaster et al. 1997, Scheffrahn et al. 1997). Acoustic emission devices are currently not commercially available. Future detection devices that may allow for the nondestructive searching of entire walls could include the use of microwaves, infrared, and laser technologies (Lewis et al. 1997).

For subterranean termites, a number of ground-based monitoring devices have been developed and used experimentally to identify and delimit the extent of colonies (Esenther & Gray 1968, La Fage et al. 1973, Tamashiro et al. 1973, Esenther & Beal 1974, 1978, Beard 1974, Esenther 1980, Su & Scheffrahn 1986a, Grace 1989, French 1991a, b, Ewart et al. 1992, Lenz & Creffield 1993, Silvestri 1996, Potter 1997b). One of these ground-based subterranean termite monitoring devices is commercially available (Su 1994a).

Subterranean Termite Control

A list of alternative strategies for subterranean termite control and selected references are provided in Table 1.

Soil termiticides. Applications of liquid termiticides to the soil, forming a chemical barrier between the structure being protected and termites below, have been the dominant means of subterranean termite control since the late 1940s. The standard measure of acceptable performance is that the chemical barrier must keep termites from penetrating 90% of the barriers for at least 5 yrs (Kard 1996a). Laboratory efficacy studies have shown all currently available organophosphate and pyrethroid soil termiticides to be effective (Su & Scheffrahn 1990b, Kard 1996a). A newer soil termiticide, imidacloprid, suggest a different mode of action toxic to termites attributed to interactions of the termiticide and a mycopathogen (Boucias et al. 1996). Although all currently registered termiticide has undergone rigorous simulated field testing, efficacy results have been mixed (Tamashiro et al. 1989, Tamashiro et al. 1990, Grace et al. 1993b, Kard 1996a). A likely cause for ineffective chemical barrier

Table 1. Summary of subtarranean termite control options.

Treatment Selected references

REMEDIAL

Soil termitiides Tamashiro et a. 1989, 1990; Su &

Scheffrahn 1990b; Smith & Rust 1990; Grace

et al. 1993b; Forschler 1994; McDaniel & Kard

1994; Boucias et al. 1996; Gold et al. 1996;

Forschler & Townsend 1996a; Kard 1996a;

Forschler & Lewis 1997

Baits Esenther & Gray 1968; Esenther & Beal 1974,

1978; Beard 1974; Esenther 1980; Su 1994b;

Su et al. 1995; Forschler & Ryder 1996; Grace

et al. 1996a; Pawson & Gold 1996; Potter et

al. 1991

Topical liquids, dusts, and Randall et al. 1934a; Grace & Abdallay 1990;

foams Su & Scheffrahn 1991a, b; Grace & Yamamoto

1992; French 1991a, b; Myles 1996; Potter et

al. 1991

Least Toxic & Nonchemical

Asphyxiant gases Delate et al. 1995b, Rust et al. 1996

Extreme temperatures Woodrow & Grace 1997, Rust & Reierson

1997, Rust et al. 1997

PREVENTIVE

Nonchemical

Particle barriers Ebeling & Pence 1957, Smith & Rust 1990,

Tamashiro et al. 1991, Su & Scheffrahn

1992, French & Ahmed 1993, Lewis et al. 1996

Metal Barriers Lenz & Runko 1993, Grace et al. 1996b, Kard

1996b

Shields Su & Scheffrahn 1990a

performance, termiticide persistence (active ingredient in ppm), has been investigated; however field results also have been mixed (Tamashiro et al. 1990, McDaniel & Kard 1994, Gold et al. 1996). Interactions between soils, termiticides, and termites can be complex and achieving a continuous and uniform treated soil barrier can be difficult (Smith & Rust 1990, Smith & Rust 1991, Forschler 1994, Forschler & Townsend 1996a, Forschler & Lewis 1997).

Baiting. Simply put, successful baiting results after the introduction of a small amount of toxicant contained in a palatable matrix that subterranean termites pass among nest mates via foraging and trophollaxis feeding leading to the death of the colony. Preliminary knowledge needed to implement any successful baiting program directed against subterranean termites is understanding their foraging behavior. The earliest studies on subterranean termite foraging behavior were for Reticulitermes spp. (Esenther & Gray 1968, Esenther & Beal 1974, 1978, Beard 1974, Esenther 1980, Howard et al. 1982) and for Heterotermes aureus from the desert southwest (Haverty et al. 1975). For these earlier works only indirect measures of colony size were possible. The development of an internal dye made colony census and levels of confidence possible (Lai 1977, Su et al. 1983). The result of this innovation saw the proliferation of mark-recapture-release studies estimating the abundance and foraging range of subterranean termites , both Reticulitermes and Heterotermes species, in wildland and urban locations (Su & Scheffrahn 1988, Grace et al. 1989b, Jones 1990, Haagsma & Rust 1995, Forschler & Townsend 1996b). Acceptance of mark-recapture-release methods for estimating subterranean termite population size and foraging range are mixed and vary from favorable (Grace 1992) to critical (Thorne et al. 1996).

The last decade has seen the rapid development of baiting technology. Laboratory screening trials have identified several toxicants as candidates to be incorporated into subterranean termite baits (Jones 1984, Haverty et al. 1989, Grace 1990, Su & Scheffrahn 1993, Su et al. 1994). The search for additional active ingredients to be incorporated into baits for subterranean termite control continues today.

The earliest field studies reporting successful control of subterranean termites by using a bait were by Esenther & Gray (1968), Beard (1974), and Esenther & Beal (1974, 1978). Wooden blocks treated with mirex suppressed Reticulitermes activity in field plots. Field successes with materials containing other active ingredients have been reported (Su 1994, Forschler & Ryder 1996c, Grace et al. 1996a).

Successful control of subterranean termites using baits have been mixed and its not clear if lack of success has been due to inadequacies of the delivery system or active ingredient (Su et al. 1995, Pawson & Gold 1996). There is also considerably disagreement among companies that develop baits and researchers on whether elimination or suppression are realistic goals for subterranean termite control (Potter 1997b) and on what a termite colony is and measures of population reduction or colony elimination (Kistner 1996). For some products there is little or no published data that the bait will perform as advertised and the disparity in performance among bait products may prove greater than with other product categories, such as conventional liquid termiticides (Potter 1997b). Areas of improved bait performance include development of additional active ingredients (Potter 1997b), modifications of bait stations (Grace et al. 1995) and the incorporation of materials to increase their appeal and retention of foragers (French 1991 a,b).

Topically applied termiticides. Historically, topically applied liquids and dusts have been reported to be effective (Randall et al. 1934a). The active ingredients reported in these earlier works were predominantly chlorinated hydrocarbons or arsenic materials formulated into dry dusts. More recently, active ingredients containing borates have dominated efficacy reporting (Grace & Abdallay 1990, Su & Scheffrahn 1991 a,b, Grace & Yamamoto 1992). French (1991 a,b) and Myles (1996) reported field success for subterranean termite control by topically applying insecticides onto foragers and releasing them back into the colony. Using topically coated foragers to introduce a toxicant into a colony is similar to baiting and assumes trophallactic passing of food throughout. A slight modification of liquid usage of termiticides, foam, has also been investigated (Potter et al. 1991). For remedial usage, the effectiveness of topically applied liquids, foams, and dusts appear to be mixed for controlling subterranean termites (Grace & Abdallay 1990, Grace & Yamamoto 1992, Myles 1996, Potter et al. 1991).

Least toxic and nonchemical methods. Laboratory trials have been conducted on the use of asphyxiant gases (i.e., CO₂ and N₂) and extreme temperature to control subterranean termites (Table 1). These studies have focused on controlling aerial subterranean termites nests. Aerial nest formation does occur among species of several genera of subterranean termites (Family: Rhinotermitidae). However, C. formosanus is frequently reported as forming aerial nests (Su & Scheffrahn 1990a). For asphyxiant gases and extreme temperatures, the reported efficacy results are very good, however, they represent laboratory

studies for C. formosanus and I. minor only (Delate et al. 1995b, Rust et al. 1996, Woodrow & Grace 1997). Extreme temperatures are from either the use of liquid nitrogen or convection heat. For liquid nitrogen, the core temperature of the individual termite must reach at least -19.5^oC to cause 100% mortality for C. formosanus (Rust & Reierson 1997, Rust et al. 1997). For heat, the minimum lethal threshold temperature for C. formosanus has been reported to be 44^{oC for 2}0 minutes (Woodrow & Grace 1997). Field verification tests for both asphyxiant and extreme temperatures are needed, especially for other species and genera of subterranean termites.

Physical barriers. Ebeling & Pence (1957) first reported the use of sand as a physical barrier for excluding subterranean termites from structures. Their findings were later reaffirmed by other laboratory (Smith & Rust 1990, Smith & Rust 1991, Tamashiro et al. 1991) and field studies (Tamashiro et al. 1991, Su & Scheffrahn 1992, Kard 1996b, Lewis et al. 1996). Field efficacy studies using sand barriers to exclude subterranean termites from structures have been mixed (Tamashiro et al. 1991, Su & Scheffrahn 1992, Kard 1996b, Lewis et al. 1996). Penetrations of sand barriers by subterranean termites was attributed to use of incorrect particle size and presence of structural irregularities (Su & Scheffrahn 1992, Lewis et al. 1996). Frequent monitoring of sites also may be needed to ensure that termites do not construct foraging tubes over barriers (Lewis et al. 1996). Other barrier materials tried to exclude subterranean termites from structures include crushed granite (French & Ahmed 1993), glass splinters (Pallaske & Igarashi 1991), and stainless steel mesh (Lenz & Runko 1993, Grace et al. 1996b, Kard 1996b). Metal shields have had mixed reports of effectiveness and diatomaceous earth is not an effective barrier against subterranean termites (Su & Scheffrahn 1990a, Grace & Yamamoto 1993).

Drywood Termite Control

Drywood termite control can be classified as whole-structure or localized treatments (Table 2). Whole-structure treatment is defined as the simultaneous treatment of all wooden members, whereas localized treatment is restricted to a group of boards or locations within boards (Scheffrahn & Su 1994). For localized treatments, accuracy in detection of and determining the extent of drywood termite infestation is critical to optimizing pest control service and providing effective treatment (for discussion on

detection methods see Termite Detection section). The discussions presented in the following sections pertain to C. brevis, I. minor, I snyderi, and M. hubbardi, the most commonly encountered drywood termite pests in structures throughout the continental United States and Hawaii.

Whole-structure treatments. Two fumigants are currently registered for drywood termite control: methyl bromide and sulfuryl fluoride (Scheffrahn & Su 1994). However, many more were previously used (Randall et al. 1934b). Fumigants are very hazardous materials and require highly specialized training in their safe use and structural preparations to prevent or minimize any disruption or damage. Fumigation is considered effective and is supported by many studies (Su & Scheffrahn 1986b, Osbrink et al. 1987, Scheffrahn & Su 1992, Lewis & Haverty 1996a). The use of a synergists, 10% CO₂, also can enhance fumigant performance (Scheffrahn et al. 1995). Desorption and residual studies for at least one of the fumigants, sulfuryl fluoride, report its safety for many household commodities if properly used and the structure is adequately aerated after treatment (Kenaga 1957, Osbrink et al. 1988, Scheffrahn et al. 1987, 1989a, 1989b). Asphyxiant gases (CO2 _{and N2}) show promise as whole-structure treatments for some drywood termite species but only laboratory studies have been conducted thus far (Delate et al. 1995b, Rust et al. 1996).

Whole-structure heating for controlling drywood termites was first reported several decades ago (Ebeling 1975). However, laboratory and large-scale field validations have only recently been reported (Ebeling 1994, Lewis & Haverty 1996a, Woodrow & Grace 1997, Rust & Reierson 1997). The heat tolerance for drywood termites appears higher than that of subterranean termites, 49^oC versus 44^oC, respectively (Rust & Reierson 1997). Whole-structure treatments with heat appear to effective. However, unsuccessful control using heat can be due to the occurrence of heat sinks. Heat sinks are areas within a structure that are more difficult to heat, for example wood on concrete (Lewis & Haverty 1996b). The use of heat is unique in being both a whole-structure and localized treatment control method (Table 2). Pretreatment preparations to prevent and minimize structural and household item damage from heat treatment have been reported (Forbes & Ebeling 1986, Ebeling 1994).

Localized treatments. The earliest localized treatments directed against drywood termites relied on arsenic containing dry dusts applied directly into drywood termite galleries (Randall et al. 1934a, Ebeling 1975). Most of those earlier materials are not registered. The effectiveness of newer chemicals

Table 2. Summary of subtarranean termite control options.

Treatment Selected references

WHOLE STRUCTURE

Fumigation Su & Scheffrahn 1986b, Osbrink et al. 1987,

Scheffrahn & Su 1992, Scheffrahn et al.

1995, Lewis & Haverty 1996a

Asphyxiant gases Delate et al. 1995b, Rust et al. 1996

Heat Ebeling 1994, Lewis & Haverty 1996a,

Woodrow & Grace 1997, Rust & Reierson 1997

LOCALIZED TREATMENTS

Chemical

Topical liquids and dusts Randall et al. 1934a, Ebeling 1975;

Scheffrahn et al. 1979, Scheffrahn & Su

1994, Scheffrahn et al. 1997

Foams ?

Liquid Nitrogen Forbes & Ebeling 1986, Lewis & Haverty

1996a, Rust & Reierson 1997, Rust et al. 1997

Nonchemical

Microwaves Lewis & Haverty 1996a

Electrocution Ebeling 1983, Lewis & Haverty 1996a

Screens, caulk, and paint ?

because of cheaper costs and possible avoidance of the disruption and expense of fumigation, localized treatments are increasingly being used (Lewis & Haverty 1996a).

A least-toxic chemical alternative to treating wood includes the use of liquid nitrogen (Table 2). Extreme cold < -20^oC is used to kill drywood termites (Rust & Reierson 1997, Rust et al. 1997). After drilling a hole near the top plate of wall voids, liquid nitrogen under pressure in large dewars is gravity fed directly into wall voids. Relative efficacy of localized treatments with liquid nitrogen are highly dosage dependent and vary from ineffective to effective (Lewis & Haverty 1996a). The limitations of this localized treatment include: many locations within structures are not treatable with this method, drilling holes damages wall coverings and wood, large amounts of liquid nitrogen may be needed, and accurately monitoring temperature changes is critical to success (Lewis & Haverty 1996a, Rust & Reierson 1997, Rust et al. 1997).

Several nonchemical methods for locally treating drywood termites are commercially available (Table 2). Two are based on elevating levels of heat: convection heat and microwaves. The effectiveness of localized convection heating in controlling drywood termites for field conditions has yet to published in refereed journals. Not unlike whole-structural heating, heat sinks may reduce the effectiveness of localized applications and care must be taken not to damage household items. The use of microwaves (700 watts), internally generated heat, to control drywood termites also has been reported (Lewis & Haverty 1996a). Effectiveness of using microwaves in controlling drywood termites was reported as mixed (Lewis & Haverty 1996a). However, more powerful devices (>10,000 watts) have been developed and their effectiveness is currently not known. Scorching can occur if the temperature of wood is not monitored during treatment (Lewis & Haverty 1996a).

High voltage electricity, or electrocution, is another nonchemical option for controlling drywood termites. The device currently marketed uses high voltage (90,000 volts) but low current (< 0.5 amps). Reported efficacy has been mixed and highly dependent on applicator technique (Ebeling 1983, Lewis & Haverty 1996a). The administration of high levels of heat is the probable cause of mortality, although the exact mode of action is not known. For maximum effects, high voltage bursts of electricity are directed at galleries containing termites. Effects can be enhanced by drilling holes and inserting metal pins into wood (Lewis & Haverty 1996a). Success also can vary depending on proximity to certain

building materials (Lewis & Haverty 1996a). The drilling of wall coverings and wood for insertion of metal pins is a destructive treatment technique.

Other nonchemical methods experientially tried against drywood termites are biological control and physical barriers, e.g., screens, caulk, and paint. There is little published information of the relative efficacy of biological control, screens, caulks, or paints directed against drywood termites (Scheffrahn & Su 1994).

Conclusions

In the past, we have used pest control strategies that provided excellent, albeit excessive termite control. We have come to expect that any new treatment will provide total elimination of termites. Clearly this is the goal of structural treatments when properties are sold (real estate transactions). However, some existing and past standards of termite control, i.e., chlordane, aldrin, dieldrin, heptachlor, methyl bromide are or will soon no longer available. Do we need to prepare the general public and pest control industry for the possibility that total elimination is not really feasible? Will the "cost" of total elimination be too great for some consumers and are they willing to accept some degradation of their structures when using localized treatments and least toxic approaches to termite control? Will we eventually adopt an IPM approach to control of termites that includes monitoring and population reduction, not elimination? These questions and more will need to be addressed before innovations in termite detection and control can effectively proceed.

Optimistically, prospects for the development of new and improvements of existing technologies as well as public acceptance of alternative termite controls appear good. Least toxic and nonchemical methods have and will continue to be developed. For subterranean termites, baits will play a major role in their control. However, materials that increase bait appeal and retention at stations are needed. Additional information needed include a more detailed understanding of subterranean foraging behavior. Advances in detection, especially those viewing entire walls nondestructively, will improve all termite control methods; whole-structure and localized treatments. The greatest challenges ahead will be securing funds for research, and identifying mechanisms for disseminating rapidly evolving information to pest control operators and consumers.

Acknowledgment

I wish to thank Drs. Kenneth Grace, Timothy Myles, Michael Rust, and Michael Potter for providing references used in the creation of this manuscript. Drs. Michael Haverty and Brian Forschler also made significant contributions to many of the ideas contained in the manuscript. Special thanks are also due to Drs. Nancy Hinkle and Faith Oi, the organizers of the Biorational Symposium, 1996 Entomological Society of America Annual meeting, Louisville, Kentucky, where this paper was presented. Lastly, I wish to thank Dr. Lisa Kala for her reviews of an earlier draft of the manuscript.

References Cited

Beard, R. L. 1974. Termite biology and the bait-block method of control. Connecticut Agriculture Experiment Station Bulletin 748. New Haven, Connecticut, 12pp.

Boucias, C. S., G. Storey & J. C. Pendland. 1996. The effects of imidacloprid on the termite Reticulitermes flavipes and its interaction with the mycopathogen Beauveria bassiana. Pfanzenschutz-Nachrichten Bayer 49: 103-144.

Delate, K. M. & J. K. Grace. 1995. Susceptibility of neem to attack by the Formosan subterranean termite, Coptotermes formosanus Shir. (Isopt., Rhinotermitidae). J. Appl. Entomol. 119: 93-95.

Delate, K. M., J. K. Grace & C. H. M. Tome. 1995a. Potential use of pathogenic fungi in baits to control the Formosan subterranean termite (Isopt., Rhinotermitidae). J. Appl. Entomol. 119: 429-433.

Delate, K. M., J. K. Grace, J. W. Armstrong & C. H. M. Tome. 1995b. Carbon dioxide as a potential fumigant for termite control. Pestic. Sci. 44: 357- 361.

Ebeling, W. & R. J. Pence. 1957. Relation of particle size to the penetration of

subterranean termites through barriers of sand or cinders. J. Econ. Entomol. 50: 690-692.

Ebeling, W. 1975. Urban entomology. University of California Press, Berkeley, California, 695 pp.

. 1983. The Extermax system for control of the western drywood termite, Incistermes minor. Etex, Las Vegas, Nevada, 11 pp.

. 1994. The thermal pest eradication system for structural pest control. The IPM Practitioner 16: 1-7.

Esenther, G. R. 1980. Estimating the size of subterranean termite colonies by a release-recapture technique. The International Research Group on Wood Preservation 11th Annual Meeting Proceedings (IRG Document No. IRG/WP/1112). IGR Secretariat, Stockholm, Sweden, 5 pp.

Esenther, G. R. & D. E. Gray. 1968. Subterranean termite studies in southern Ontario. Can. Entomol. 100: 827-834.

Esenther, G. R. & R. H. Beal. 1974. Attractant-mirex bait suppresses activity of Reticulitermes spp. J. Econ. Entomol. 67: 85-88.

. 1978. Insecticidal baits on field plot perimeters suppress Reticulitermes. J. Econ. Entomol. 71: 604-607.

Ewart, D. McG., J. K. Grace, R. T. Yamamoto & M. Tamashiro. 1992. Hollow stakes for detecting subterranean termites (Isoptera: Rhinotermitidae). Sociobiology 20: 17-22.

Forbes, C. A. & W. Ebeling. 1986. Update: liquid nitrogen controls drywood termites. The IPM

Practitioner 8: 1-4.

Forschler, B. T. 1994. Survivorship and tunneling activity of Reticulitermes flavipes (kollar) (Isoptera: Rhinotermitidae) in response to termiticide soil barriers with and without gaps of untreated soil. J. Entomol. Sci. 29: 43-54.

Forschler, B. T. & M. L. Townsend. 1996a. Mortality of eastern subterranean termites (Isoptera: Rhinotermitidae) exposed to four soils treated with termiticides. J. Econ. Entomol. 89: 678-681.

. 1996b. Mark-release-recapture estimates of Reticulitermes spp. (Isoptera: Rhinotermitidae) colony foraging populations from Georgia, U.S.A. Environ. Entomol. 25: 952-962.

Forschler, B. T. & J. C. Ryder, Jr. 1996c. Subterranean termite, Reticulitermes spp. (Isoptera: Rhinotermitidae), colony response to baiting with hexaflumuron using a prototype commercial termite baiting system. J. Entomol. Sci. 31: 143-151.

Forschler, B. T. & V. R. Lewis. 1997. Soils, termiticides, and termites: their interaction and what it means to control. Pest Control 65: 42-46 & 53.

French, J. R. J. 1991a. Baits and foraging behavior of Australian species of Coptotermes. Sociobiology 19: 171-186.

. 1991b. Baiting techniques for control of Coptotermes species within existing buildings, pp. 46-50. In M. I. Haverty & W. W. Wilcox (technical coordinators), Proceedings of the symposium on current research on wood-destroying organisms and future prospects for protecting wood in use. USDA Forest Service Gen. Tech. Rep. PSW- 128, 65 pp.

French, J. R. J. & B. Ahmed. 1993. Termite physical barriers: is retrofitting with Granitgard an option? The International Research Group on Wood Preservation 24th Annual Meeting Proceedings (IRG Document No. IRG/WP/93-40011). IGR Secretariat, Stockholm, Sweden, 9 pp.

Fujii, Y. M. Noguchi, Y. Imamura & M. Tokoro. 1990. Using acoustic emission monitoring to detect termite activity in wood. Forest Prod. J. 40: 34-36.

Gold, R. E., H. N. Howell, Jr., B. M. Pawson, M. S. Wright & J. C. Lutz. 1996. Persistence and bioavailability of termiticides to subterranean termites(Isoptera: Rhinotermitidae) from five soil types and locations in Texas. Sociobiology 28: 337-363.

Grace, J. K. 1989. A modified trap technique for monitoring Reticulitermes subterranean termite populations (Isoptera: Rhinotermitidae). Pan- Pac. Entomol. 65: 381-384.

. 1990. Oral toxicity of barium metaborate to the eastern subterranean termite (Isoptera: Rhinotermitidae). J. Entomol. Sci. 25: 112-116.

. 1992. Termite distribution, colony size, and potential for damage, pp. 67-76. In Proceedings of the National Conference on Urban Entomology, 23-26 February, 1992, University of Maryland, College Park, Maryland. Virginia Polytechnic Institute, Blacksburg, Virginia, 179 pp.

_______. 1997. Termite resistance of pine wood treated with chromated copper arsenate. The International Research Group on Wood Preservation 28th Annual Meeting Proceedings (IRG Document No. IRG/WP/97). IRG Secretariat, Stockholm, Sweden, 7 pp.

Grace, J. K. & A. Abdallay. 1990. Termiticidal activity of boron dusts (Isoptera, Rhinotermitidae). J. Appl. Entomol. 109: 283-288.

Grace, J. K. & R. T. Yamamoto. 1992. Termiticidal effects of a glycol borate wood surface treatment. Forest Prod. J. 42: 46-48.

. 1993. Diatomaceous earth is not a barrier to Formosan subterranean termites (Isoptera: Rhinotermitidae). Sociobiology 23: 25-30.

. 1994. Natural resistance of Alaska-cedar, redwood, and teak to Formosan subterranean termites. Forest Prod. J. 44: 41-45.

Grace, J. K., D. L. Wood & G. W. Frankie. 1989a. Behavior and survival of Reticulitermes hesperus Banks (Isoptera: Rhinotermitidae) on selected sawdusts and wood extracts. J. Chem. Ecol. 15: 129-139.

Grace, J. K., A. Abdallay & K. R. Farr. 1989b. Eastern subterranean termite (Isoptera: Rhinotermitidae) foraging territories and populations in Toronto. Can. Entomol. 121: 551-556.

Grace, J. K., R. T. Yamamoto & P. E. Laks. 1993a. Laboratory evaluation of copper naphthenate pressure treatments against the Formosan subterranean termite. The International Research Group on Wood Preservation 24th Annual Meeting Proceedings (IRG Document No. IRG/WP/93-10005). IGR Secretariat, Stockholm, Sweden, 10 pp.

Grace, J. K., J. R. Yates & M. Tamashiro. 1993b. Testing soil insecticides in paradise. Pest Control 61: 60-61.

Grace, J. K., J. R. Yates & C. H. M. Tome. 1995. Modification of a commercial bait station to collect large numbers of subterranean termites (Isoptera: Rhinotermitidae). Sociobiology 26: 259-268.

Grace, J. K., C. H. M. Tome, T. G. Shelton, R. J. Oshiro & J. R. Yates III. 1996a. Baiting studies and considerations with Coptotermes formosanus (Isoptera: Rhinotermitidae) in Hawaii. Sociobiology 28:

511-520.

Grace, J. K., J. R. Yates III, C. H. M. Tome & R. J. Oshiro. 1996b. Termite-resistant construction: use of a stainless steel mesh to exclude Coptotermes formosanus (Isoptera: Rhinotermitidae). Sociobiology 28: 365-372.

Haagsma, K. A. & M. K. Rust. 1995. Colony size estimates, foraging trends, and physiological characteristics of the western subterranean termite (Isoptera: Rhinotermitidae). Environ. Entomol. 24: 1520-1528.

Haverty, M. I. & L. J. Nelson. 1997. Cuticular hydrocarbons of Reticulitermes (Isoptera: Rhinotermitidae) from Northern California indicate undescribed species. Comp. Biochem. Physiol. B. (In Press).

Haverty, M. I., W. L. Nutting & J. P. La Fage. 1975. Density of colonies and spatial distribution of foraging territories of the desert subterranean termite, Heterotermes aureus (Snyder). Environ. Entomol. 4: 105-109.

Haverty, M. I., N.-Y. Su, M. Tamashiro & R. Yamamoto. 1989. Concentration-dependent presoldier induction and feeding deterrency: potential of two insect growth regulators for remedial control of the Formosan subterranean termite (Isoptera: Rhinotermitidae). J. Econ. Entomol. 82: 1370-1374.

Haverty, M. I., B. T. Forschler & L. J. Nelson. 1996. An assessment of the taxonomy of Reticulitermes (Isoptera: Rhinotermitidae) from the Southeastern United States based on cuticular hydrocarbons.

Sociobiology 28: 287-318.

Howard, , R. W., S. C. Jones, J. K. Mauldin & R. H. Beal. 1982. Abundance, distribution, and colony size estimates for Reticulitermes spp. (Isoptera: Rhinotermitidae) in southern Mississippi. Environ. Entomol. 11: 1290-1293.

Hyvernaud, M., F. Wiest, M. M. Serment, M. Angulo & O. Winkel. 1996. Make ready of a detection system for insect attack by acoustical method. The International Research Group on Wood Preservation 27th Annual Meeting Proceedings (IRG Document No. IRG/WP 96-10183). IGR Secretariat, Stockholm, Sweden, 9 pp.

Jones, S. C. 1984. Evaluation of two insect growth regulators for the bait-block method of subterranean termite (Isoptera: Rhinotermitidae) control. J. Econ. Entomol. 77: 1086-1091.

_______. 1990. Delineation of Heterotermes aureus (Isoptera: Rhinotermitidae) foraging territories in a Sonoran desert grassland. Environ. Entomol. 19: 1047-1054.

Kard, B. M. 1996a. 1996 Gulfport update termiticide field tests. Pest Control 64: 45, 46, 48 & 92.

_______. 1996b. High-grade stainless-steel mesh and sand-barrier field tests for control of subterranean termites. Abstract from the Proceedings of The National Conference on Urban Entomology, February 18-20, 1996, Arlington, Texas, 1 pp.

Kenaga, E. E. 1957. Some biological, chemical and physical properties of sulfuryl fluoride as an insecticidal fumigant. J. Econ. Entomol. 50: 1-6.

Kistner, D. H. 1996. Summary of the North American termite biology and control conference. Sociobiology 28: 531-534.

La Fage, J. P., W. L. Nutting & M. I. Haverty. 1973. Desert subterranean termites: A method for studying foraging behavior. Environ. Entomol. 2: 954-956.

Lai, P. Y. 1977. Biology and ecology of the Formosan subterranean termite, Coptotermes formosanus, and its susceptibility to the entomogenous fungi, Beauveria bassiana and Metarrhizium anisopliae. Ph.

D. diss., Univ. of Hawaii, Honolulu, HI.

Lemaster, R. L., F. C. Beall & V. R. Lewis. 1997. Detection of termites with acoustic emission. Forest Prod. J. 47: 75-79.

Lenz, M. & J. W. Creffield. 1993. A below-ground exposure method for determining the resistance of woody and non-woody materials to attack by subterranean termites. The International Research Group on Wood Preservation 11th Annual Meeting Proceedings (IRG Document No. IRG/WP/93-10012). IGR Secretariat, Stockholm, Sweden, 16 pp.

Lenz, M. & S. Runko. 1993. Protection of buildings, other structures and materials in ground contact from attack by subterranean termites with a physical barrier- a fine mesh of high grade stainless steel. The International Research Group on Wood Preservation 24th Annual Meeting Proceedings (IRG Document No. IRG/WP/93-10014). IGR Secretariat, Stockholm, Sweden, 10 pp.

Lewis, V. R. & R. L. Lemaster. 1991. The potential of using acoustical emission to detect termites within wood, pp. 34-37. In M. I. Haverty & W. W. Wilcox (technical coordinators), Proceedings of the symposium on current research on wood-destroying organisms and future prospects for protecting wood in use. USDA Forest Service Gen. Tech. Rep. PSW-128, 65 pp.

Lewis, V. R. & M. I. Haverty. 1996a. Evaluation of six techniques for control of the western drywood termite (Isoptera: Kalotermitidae) in structures. J. Econ. Entomol. 89: 922-934.

. 1996b. Long awaited nonchemical alternative to drywood termite control study completed. The Voice of PCOC, Summer 1996, pp. 20-22, 24, 26, 28-29.

Lewis, V. R., M. I. Haverty, D. S. Carver & C. Fouche. 1996. Field comparison of sand or insecticide barriers for control of Reticulitermes spp. (Isoptera: Rhinotermitidae) infestations in homes in Northern

California. Sociobiology 28: 327-336.

Lewis, V. R., C. F. Fouche & R. L. Lemaster. 1997. Evaluation of dog-assisted searches and electronic odor devices for detecting the western subterranean termite (Isoptera: Rhinotermitidae). Forest Prod. J. (In Press).

Mauldin, J. K. & R. H. Beal. 1989. Entomogenous nematodes for control of subterranean termites, Reticulitermes spp. (Isoptera: Rhinotermitidae). J. Econ. Entomol. 82: 1638-1642.

McDaniel, C. A. & B. M. Kard. 1994. The latest in termiticide degradation. Pest Control Technology 22: 80, 84, 86, 90-91.

Myles, T. G. 1996. Development and evaluation of a transmissible coating for control of subterranean termites. Sociobiology 28: 373-457.

Osbrink, W. L. A., R. H. Scheffrahn, N.-Y. Su & M. K. Rust. 1987. Laboratory comparisons of sulfuryl fluoride toxicity and mean time of mortality among ten termite species (Isoptera: Hodotermitidae, Kalotermitidae, Rhinotermitidae). J. Econ. Entomol. 80: 1044-1047.

Osbrink, W. L. A., R. H. Scheffrahn, R.-C. Hsu & N.-Y. Su. 1988. Sulfuryl fluoride residues of fumigated foods protected by polyethylene film. J. Agric. Food Chem. 36: 853-855.

Pallaske, M. & A. Igarashi. 1991. Glass splinters as physical termite barriers: optimized material properties in use with and without insecticidal pretreatment minimizes environmental contaminations. The International Research Group on Wood Preservation 22th Annual Meeting Proceedings (IRG Document No. IRG/WP/1476). IGR Secretariat, Stockholm, Sweden, 14 pp.

Pawson, B. M. & R. E. Gold. 1996. Evaluation of baits for termites (Isoptera: Rhinotermitidae) in

Texas. Sociobiology 28: 485-510.

Potter, M. F. 1997a. Termites. In Mallis Handbook of Pest Control, 8th Ed., A. Mallis. Cleveland: Franzak & Foster Co.

________. 1997b. Termite baits:status report. Pest Control Technology 25: 24-26, 28, 30, 35-37, 97, 105-106, 110.

Potter, M. F., J. P. Hardy & S. E. Richardson. 1991. New termite tool: foam. Pest Control 59: 72, 73, 76, 77.

Randall, M., W. B. Herms & T. C. Doody. 1934a. The toxicity of chemicals to termites, pp. 340-356. In Kofoid, C. A. (Ed.), Termites and termite control. University of California Press, Berkeley, California, 795 pp.

Randall, M., T. C. Doody & B. Weidenbaum. 1934b. Treatment by fumigation, pp. 450-471. In Kofoid, C. A. (Ed.), Termites and termite control. University of California Press, Berkeley, California, 795 pp.

Rust, M. K. & R. H. Scheffrahn. 1982. Performance of treated surfaces against western drywood termites. Insect. Acari. 7: 234-235.

Rust, M. K., J. M. Kennedy, V. Daniel, J. R. Druzik & F. D. Preusser. 1996. The feasibility of using modified atmospheres to control insect pests in

museums. Restaurator 17: 43-60.

Rust, M. K. & D. A. Reierson. 1997. Use of extreme temperatures in urban insect pest management. In G. J. Hallman & D. L. Denlinger [Eds.], Lethal temperatures in integrated pest management.

Westview Press, Boulder, Colorado. (In Press).

Rust, M. K., E. O. Paine & D. A. Reierson. 1997 Evaluation of freezing to control wood-destroying insects (Isoptera, Coleoptera). J. Econ. Entomol. (In Press).

Scheffrahn, R. H. 1991. Allelochemical resistance of wood to termites. Sociobiology 19: 257-281.

Scheffrahn, R. H. & N.-Y. Su. 1992. Comparative toxicity of methyl bromide against ten nearctic termite species (Isoptera: Termopsidae, Kalotermitidae, Rhinotermitidae). J. Econ. Entomol. 85: 845-847.

. 1994. Control of drywood termites (Isoptera: Kalotermitidae), pp. 41-54. In W. H. Robinson [Ed.], Proceedings of the National Conference on Urban Entomology, Atlanta, Georgia, 139 pp.

Scheffrahn, R. H., M. K. Rust & D. A. Reierson. 1979. Evaluation of insecticides for wester drywood termite control. Insect. Acari. 4: 205.

Scheffrahn, R. H., W. L. A. Osbrink, R.-C. Hsu & N.-Y. Su. 1987. Desorption of residual sulfuryl fluoride from structural and household commodities by headspace analysis using gas chromatography. Bull. Environ. Contam. Toxicol. 39: 769-775.

Scheffrahn, R. H., R.-C. Hsu & N.-Y. Su. 1989a. Fluoride residues in frozen foods fumigated with sulfuryl fluoride. Bull. Environ. Contam. Toxicol. 43: 899-903.

Scheffrahn, R. H., R.-C. Hsu, W. L. A. Osbrink & N.-Y. Su. 1989b. Fluoride and sulfate residues in foods fumigated with sulfuryl fluoride. J. Agric. Food Chem. 37: 203-206.

Scheffrahn, R. H., W. P. Robbins, P. Busey, N.-Y. Su & R. K. Mueller. 1993. Evaluation of a novel, hand-held, acoustic emissions detector to monitor termites (Isoptera: Kalotermitidae, Rhinotermitidae) in wood. J. Econ. Entomol. 86: 1720-1729.

Scheffrahn, R. H., G. S. Wheeler & N.-Y. Su. 1995. Synergism of methyl bromide and sulfuryl fluoride toxicity against termites (Isoptera: Kalotermitidae, Rhinotermitidae) by admixture with carbon dioxide. J. Econ. Entomol. 88: 649-653.

Scheffrahn, R. H., N.Y. Su & P. Busey. 1997. Laboratory and field evaluations of selected chemical treatments for control of drywood termites (Isoptera: Kalotermitidae). J. Econ. Entomol. 90: 492-502.

Silvestri, S. 1996. Innovative termite bait technology saves building and business. Pest Control 64: 64, 65, 68.

Smith, J. L. & M. K. Rust. 1990. Tunneling response and mortality of the western subterranean termite (Isoptera: Rhinotermitidae) to soil treated with termiticides. J. Econ. Entomol. 83: 1395-1401.

. 1991. Factors affecting the tunneling behavior of the western subterranean termite, Reticulitermes hesperus Banks, pp. 28-33. In M. I. Haverty & W. W. Wilcox (technical coordinators), Proceedings of the symposium on current research on wood-destroying organisms and future prospects for protecting wood in use. USDA Forest Service Gen. Tech. Rep. PSW- 128, 65 pp.

Su, N.-Y. 1994a. The termite bait age dawns. Pest Control 6: 36-38.

______. 1994b. Field evaluation of a hexaflumuron bait for population suppression of subterranean termites (Isoptera: Rhinotermitidae). J. Econ. Entomol. 87: 389-397.

Su, N.-Y. & R. H. Scheffrahn. 1986a. A method to access, trap, and monitor field populations of the

Formosan subterranean termite (Isoptera: Rhinotermitidae) in the urban environment. Sociobiology 12: 299-304.

. 1986b. Field comparison of sulfuryl fluoride susceptibility among three termite species (Isoptera: Kalotermitidae, Rhinotermitidae) during structural fumigation. J. Econ. Entomol. 79: 903-908.

. 1988. Foraging population and territory of the Formosan subterranean termite (Isoptera: Rhinotermitidae) in an urban environment. Sociobiology 14: 353-359.

. 1990a. Economically important termites in the United States and their control. Sociobiology 17: 77-94.

. 1990b. Comparison of eleven soil termiticides against the Formosan subterranean termite and Eastern subterraneantermite (Isoptera: Rhinotermitidae). J. Econ. Entomol. 83: 1918-1924.

. 1991a. Remedial wood preservative efficacy of Bora-Care® against the Formosan subterranean termite and Eastern subterranean termite (Isoptera: Rhinotermitidae). The International Research Group on Wood Preservation 22th Annual Meeting Proceedings (IRG Document No. IRG/WP/1504). IRG Secretariat, Stockholm, Sweden, 7 pp.

. 1991b. Laboratory evaluation of disodium octaborate tetrahydrate (Tim-Bor®) as a wood preservative or a bait- toxicant against the Formosan and Eastern subterranean termite (Isoptera: Rhinotermitidae). The International Research Group on Wood Preservation 22th Annual Meeting Proceedings (IRG Document No. IRG/WP/1513). IRG Secretariat, Stockholm, Sweden, 12 pp.

. 1992. Penetration of sized particle barriers by field populations of subterranean termites (Isoptera: Rhinotermitidae). J. Econ. Entomol. 85: 2275-2278.

. 1993. Laboratory evaluation of two chitin synthesis inhibitors, hexaflumuron and diflubenzuron, as bait toxicants against Formosan and eastern subterranean termites